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{\bf Rui Xu and Cun-Quan Zhang}
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{\bf Nowhere-Zero 3-Flows in Squares of Graphs}
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It was conjectured by Tutte that every 4-edge-connected graph admits
a nowhere-zero $3$-flow. In this paper, we give a complete
characterization of graphs whose squares admit nowhere-zero
$3$-flows and thus confirm Tutte's $3$-flow conjecture for the
family of squares of graphs.


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